Troublesome Audio Research DSi200

For any of you who have owned, or may still own this integrated amp, have you experienced issues with it? I bought mine used last year to supplant a Hegel H200 that was a little too bright for my taste and sucked rather a lot of electricity out of the wall even when in standby. In general I have liked the sound of the DSi200 but it does present a very slight hum through the speakers, a bit louder in the left channel than the right. After having it serviced TWICE, once by ARC and once by an different authorized service provider to address this issue, I am told that it's an artifact of class D amplification (high frequency switching) and so I guess that's just what this amp does. It's a soft hum and you really have to have your ear right up to the speaker to hear it.

Since it came back from its last service, it has been mostly sitting in its box (I'm currently using a Modwright KWI200) but today I took it out to do a little comparative listening because at some point I have to decide which of these amps to keep and which to sell. I thought that letting it run for a good week or so would insure that it's in full voice, but a few hours in, it began to buzz very loudly--the amplifier, not the speakers. Since I'm not an electrical engineer (far from it!) I really don't know what is causing this. I'd hate to go the trouble and expense of having it serviced a third time in less than a year, but obviously I can't sell it in this condition. Any theories about this? Have any of you had this happen? I'd be very grateful to hear your experiences. Thanks.
I'm not familiar with this particular component but the last time I heard a buzz from an amplifier itself, it was coming from the power transformer. If possible, put your ear close to the transformer and see if its from that area. You may also want to make sure the transformer is tightly screwed down to the chassis by inspecting it unplugged and with the cover removed. Good luck.
A belated thanks, kalali, for your reponse. I'd rather have an authorized service tech do this, owing to my lack of technical knowledge.  I have contacted ARC about this, and though I have received an initial response, things move slowly there so it's liable to be a while before this gets remedied. The last time I sent this amp to them it was nearly 2 months before I saw it again and that only because I sort of nagged them about it. I'll keep on it and post an update when I have news.
Update: I had the amplifier repaired by an authorized ARC service provider and fortunately it didn't involve replacing the transformer, which isn't available any more anyway. They applied a new coat of lacquer and anchored the transformer more firmly. Problem seems to be solved, permanently, I hope.
Hi cooper52,

I own an dsi200 as well for about 2 years, and lately it also buzz, or produce such sound exactly, exactly like what you described.

Can you tell me a bit more on how to fix it? Because from my dealer in order to replace the transformer it take usd1200, which is not accepable to me.

The DS (digital switching) Audio Research amps are their worst sounding amps ever!
Glad you are insulting these peoples amps
koonyur, here is what the repair involved, quoted from my invoice:
"Power transformer not available from ARC. Removed Power Transformer used a high grade lacquer to reseal unit applied caulking, and bench tested for 3 weeks."

It has been working trouble-free ever since so it appears this repair was successful. Including shipping, it cost me about $500 USD.